In this paper

TiAl based alloy with composition of Ti-47Al-2Cr-2Nb has been successfully prepared by electromagnetic cold crucible directional solidification. The microstructure of the directionally solidified alloy consisted of alternatively arranged lamellae which were composed of α2+γ laths. The inter-lamellar spacing was influenced by withdrawal rate and thinner inter-lamellar spacing was achieved at higher withdrawal rate. The included angels between columnar crystal orientation and the growth direction increase with the increasing withdrawal rate. The high temperature tensile properties were tested from 600℃ to 800℃ and the fracture strength of the alloy decreased with the increasing test temperature. Inter-lamellar spacing was a significant influence factor on the high temperature tensile strength and the alloy prepared at withdrawal rate of 1.2mm/min showed the highest strength (470MPa) at 800℃ . The α2/γ interfaces in the fully lamellar structure could act as obstacles to shearing. Higher density of interfaces existed in the matrix of the alloy with higher withdrawal rates and greater applied stress was essential for further deformation in case of thinner inter-lamellar spacing. A function of tensile strength and test temperature was created according to the values of alloy prepared at withdrawal rate of 1.0 mm/min from 600℃ to 800℃ . The effect of withdrawal rate on the stress rupture-properties was investigated at 200MPa/650℃ . The results showed that finer inter-lamellar spacing could enhance the high temperature stress ruptureproperties. Under the same test conditions

the alloy prepared at withdrawal rate of 1.2mm/min held the highest creeprupture life (48h). The improvement effect of thinner lamellar structure on creep-rupture life decreased with the increasing test temperature and applied stress. The fracture morphology of the stress-rupture samples indicated the Ti-47Al-2Cr-2Nb behaved in brittle cleavage fracture companied with a small amount of ductile fracture. The predication model of the stressrupture was set up through Larson-Miller and Manson-Haferd parametric method. The predication function is an accurate model confirmed by little difference existing between theoretical and experimental values.